Perspectives

The Importance of Synchronization During Routine Cardioversion of Atrial Fibrillation

View the perspectives from an EP physician and EP nurse as they discuss this case of synchronization.

Joan M. Copeland, BSN, RN, Akron General Medical Center, Akron, Ohio

Figure 1. This figure demonstrates the induction of ventricular fibrillation via a spurious shock administered from a unsynchronized cardioversion attempt. The electrical shock fell in the vulnerable period of the T wave and provoked ventricular fibrillation which terminated spontaneously. The importance of this is to remember to depress the synchronization button on a standard defibrillator.

Discussion: This case study demonstrates the importance of the synchronization mode during cardioversions. Synchronization is everyone's responsibility. Once the synchronization button is on, a marker appears on every QRS complex. Remembering to look for these markers reduces the chance of inappropriate defibrillations. Each person in the room needs to get in the habit of glancing at the monitor to verify that the markers are indeed present. In our lab, we give Brevital to patients who are being cardioverted. Waiting for this to take effect allows us time to turn on the synchronization button and charge the defibrillator. Routine cardioversions are not emergencies.

Some defibrillators default to the unsynchronized mode after each shock while others will stay in the synchronized mode until one manually pushes the button. It is imperative to know how the defibrillator used in your lab functions. This would mean that if the patient would go into a pulseless ventricular tachycardia or fibrillation, one would need to manually turn off the synchronization button in order for the defibrillator to fire.

In general, the rule of thumb that I teach ACLS students is "if you have a pulse, you need to synchronize; if you have no pulse, there is no synchronization." Although there are a few exceptions to this rule, this seems to help them remember quickly whether or not to use the synchronization button.

Todd J. Cohen, MD, Winthrop-University Hospital , Mineola, NY

The technique for appropriate cardioversion has been well described. It is important to synchronize the electrical shock to the QRS complex such that the discharge does not fall in the vulnerable period of the T-wave and provoke ventricular fibrillation.

Case in point: A 28-year-old woman with atrial fibrillation was referred for elective cardioversion. The patient was hooked up to an external monitoring defibrillator and informed consent was obtained. During discharge of the electrical shock, the button on the defibrillator failed to be deployed without synchronization and the following event occurred. Figure 1 shows atrial fibrillation followed by a 50 joule shock in the vulnerable period of the T-wave, which resulted in ventricular fibrillation. The episode terminated spontaneously without events.

Discussion. It is important to know that every modern day defibrillator has a synchronization button. This button needs to be depressed and reset after every synchronized shock. Without depressing this button, there is a certain probability that a shock deployed may randomly fall within the vulnerable period of the T wave. For a standard calculation of this, assuming a heart rate of 60 beats per minute or 1,000 msec cycle length, and assuming that the vulnerable period of the T wave is approximately 150 msec, there would be a 15% chance of a random shock falling within the vulnerable period of the T wave. Using this type of an analysis, one can summarize that it is prudent to always depress the synchronize button when performing a cardioversion. We at Winthrop have performed thousands of cardioversions without this event; however, even in a busy laboratory with heavy through put, one may find the spurious incident of inappropriate discharge from a failed cardioversion. The conclusion of this "Back to Basics" session is that synchronization is very important and should be a standard check-off prior to elective cardioversion.